Constrained liner locking ring and polyethylene liner congruency feature

ABSTRACT

One embodiment of the present invention relates to a prosthesis, comprising: an acetabular cup, wherein the cup has an open end and a closed end, wherein the open end of the cup is defined by a rim and wherein the rim has an outer facing surface; at least one cavity disposed in the rim, wherein the cavity extends from a first end of the cavity at the outer facing surface to a second end of the cavity that is towards the closed end of the cup, and wherein the cavity comprises an undercut at the second end of the cavity; a locking ring; and at least one tab extending from the locking ring, wherein the tab comprises a first leg and a second leg having a separation therebetween, wherein each leg has a first end and a second end, wherein the first end of each leg is at the locking ring, wherein the second end of the first leg comprises a tab protrusion, and wherein at least the second leg is resilient such that the separation between the first leg and the second leg is reduced when the second leg is deflected towards the first leg; wherein the locking ring is removably locked to the cup by placement of the locking ring adjacent the rim and insertion of the tab into the cavity such that the second leg presses against a sidewall of the cavity to initially deflect the second leg towards the first leg as the tab enters the cavity and the tab protrusion of the first leg is urged into the undercut by the second leg subsequently deflecting back away from the first leg.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Ser.No. 60/869,694, filed Dec. 12, 2006, which is incorporated herein byreference in its entirety.

FIELD OF THE INVENTION

One embodiment of the present invention relates to a constrained linerlocking ring.

Another embodiment of the present invention relates to a polyethyleneliner congruency feature.

For the purposes of describing and claiming the present invention, theterm “resilient” (e.g., resilient leg) is intended to refer to acomponent that may be deflected in a first direction in response to theapplication of a force and then springs back (at least partially) in asecond direction that is essentially opposite to the first directionwhen the force is removed.

BACKGROUND OF THE INVENTION

A conventional prosthesis (e.g., for use in connection with total hiparthroplasty) includes an acetabular cup, constrained liner and lockingring.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of an acetabular cup (cluster hole, poly/diamond,52 mm, group 2) according to an embodiment of the present invention;

FIG. 2 is a plan view of the acetabular cup of FIG. 1;

FIG. 3 is a side view (in cross-section) of the acetabular cup of FIG.1;

FIG. 4 is another side view (in cross-section) of the acetabular cup ofFIG. 1;

FIG. 5 shows section C-C with reference to FIG. 2;

FIG. 6 shows detail D with reference to FIG. 5;

FIG. 7 shows detail E with reference to FIG. 3;

FIG. 8 shows detail F with reference to FIG. 3;

FIG. 9 shows detail G with reference to FIG. 2;

FIG. 10 shows detail H with reference to FIG. 1;

FIG. 11 shows detail J with reference to FIG. 10;

FIG. 12 is another plan view of the acetabular cup of FIG. 1;

FIG. 13 is another plan view of the acetabular cup of FIG. 1;

FIG. 14 is a side view of an acetabular cup (cluster hole, poly/diamond,48 mm, group 1) according to another embodiment of the presentinvention;

FIG. 15 is a plan view of the acetabular cup of FIG. 14;

FIG. 16 is a side view (in cross-section) of the acetabular cup of FIG.14;

FIG. 17 is another side view (in cross-section) of the acetabular cup ofFIG. 14;

FIG. 18 shows section C-C with reference to FIG. 15;

FIG. 19 shows detail D with reference to FIG. 18;

FIG. 20 shows detail E with reference to FIG. 16;

FIG. 21 shows detail F with reference to FIG. 16;

FIG. 22 shows detail G with reference to FIG. 15;

FIG. 23 shows detail H with reference to FIG. 14;

FIG. 24 shows detail J with reference to FIG. 23;

FIG. 25 is another plan view of the acetabular cup of FIG. 14;

FIG. 26 is another plan view of the acetabular cup of FIG. 14;

FIG. 27 is a plan view of constrained liner locking ring according toanother embodiment of the present invention;

FIG. 28 is another plan view of the constrained liner locking ring ofFIG. 27;

FIG. 29 is a side view of the constrained liner locking ring of FIG. 27;

FIG. 30 is another side view of the constrained liner locking ring ofFIG. 27;

FIG. 31 shows detail B with reference to FIG. 29;

FIG. 32 shows detail A with reference to FIG. 28;

FIG. 33 shows detail E with reference to FIG. 29;

FIG. 34 shows section D-D with reference to FIG. 28;

FIG. 35 is a plan view of a constrained liner (28 mm, group 1, 48/50 mmcups) according to another embodiment of the present invention;

FIG. 36 is another plan view of the constrained liner of FIG. 35;

FIG. 37 is side view (in cross-section) of the constrained liner of FIG.35;

FIG. 38 shows section C-C with reference to FIG. 35;

FIG. 39 shows detail E with reference to FIG. 37;

FIG. 40 shows detail F with reference to FIG. 38;

FIG. 41 shows detail B with reference to FIG. 36;

FIG. 42 shows detail D with reference to FIG. 37;

FIG. 43 shows another side view of the constrained liner of FIG. 35;

FIG. 44 is a plan view of a constrained liner (32 mm, group 2, 52/54 mmcups) according to another embodiment of the present invention;

FIG. 45 is another plan view of the constrained liner of FIG. 44;

FIG. 46 is side view (in cross-section) of the constrained liner of FIG.44;

FIG. 47 shows section C-C with reference to FIG. 44;

FIG. 48 shows detail E with reference to FIG. 46;

FIG. 49 shows detail F with reference to FIG. 47;

FIG. 50 shows detail B with reference to FIG. 45;

FIG. 51 shows detail D with reference to FIG. 46;

FIG. 52 shows another side view of the constrained liner FIG. 44;

FIG. 53 is a plan view of an acetabular cup according to an embodimentof the present invention;

FIG. 54 is a plan view of a constrained liner locking ring according toan embodiment of the present invention;

FIG. 55 shows certain details of a tab for locking the locking ring ofFIG. 54 to the cup of FIG. 53;

FIG. 56 is a cross-sectional view showing certain details of atab/undercut locking mechanism for locking the locking ring of FIG. 54to the cup of FIG. 53;

FIG. 57 is a plan view of a constrained liner locking ring according toan embodiment of the present invention;

FIG. 58 shows section A-A with reference to FIG. 57;

FIG. 59 shows certain details of a tab for locking the locking ring ofFIG. 54 to the cup of FIG. 53;

FIG. 60 shows certain details of a tab for locking the locking ring ofFIG. 54 to the cup of FIG. 53;

FIG. 61 shows certain details of a cavity undercut in an acetabular cupused in connection with locking the locking ring of FIG. 54 to the cupof FIG. 53;

FIG. 62 shows a cross-section of a prosthesis according to anotherembodiment of the present invention;

FIG. 63 shows a plan view of an example locking ring of the type used inconnection with the prosthesis of FIG. 62;

FIG. 64 shows another plan view of an example locking ring of the typeused in connection with the prosthesis of FIG. 62;

FIG. 65 is a plan view of an acetabular cup according to an embodimentof the present invention;

FIG. 66 shows a cross-section of an example interference fit feature ofthe acetabular cup of FIG. 65;

FIG. 67 shows another cross-section of an example interference fitfeature of the acetabular cup of FIG. 65; and

FIG. 68 shows a cross-section of an example interference fit feature ofa polyethylene liner according to an embodiment of the presentinvention.

Of note, a feature may be identified by a reference number in aparticular figure. In other figures, a similar feature may be identifiedby the same reference number, with the addition of an alphabetic suffix(such similar elements may differ in size and/or shape details as shownin the drawings).

Among those benefits and improvements that have been disclosed, otherobjects and advantages of this invention will become apparent from thefollowing description taken in conjunction with the accompanyingfigures. The figures constitute a part of this specification and includeillustrative embodiments of the present invention and illustrate variousobjects and features thereof.

DETAILED DESCRIPTION OF THE INVENTION

Detailed embodiments of the present invention are disclosed herein;however, it is to be understood that the disclosed embodiments aremerely illustrative of the invention that may be embodied in variousforms. In addition, each of the examples given in connection with thevarious embodiments of the invention is intended to be illustrative, andnot restrictive. Further, the figures are not necessarily to scale, somefeatures may be exaggerated to show details of particular components(and any size, material and similar details shown in the figures are, ofcourse, intended to be illustrative and not restrictive). Therefore,specific structural and functional details disclosed herein are not tobe interpreted as limiting, but merely as a representative basis forteaching one skilled in the art to variously employ the presentinvention.

As described herein, one embodiment of the present invention provides aconstrained liner locking ring that can easily be implanted.

Further, another embodiment of the present invention provides aconstrained liner locking ring in which proper mating with theacetabular cup can be confirmed.

Further still, another embodiment of the present invention provides aconstrained liner locking ring which can easily be removed (e.g., toaddress the need for a revision). Such removal may be carried out, forexample, by providing a clockwise or counter-clockwise motion todisengage a locking feature from the acetabular cup.

Further still, another embodiment of the present invention provides aconstrained liner locking ring that can be used in connection with atotal hip arthroplasty and that may be easily assembled and disassembled(as required).

Further still, another embodiment of the present invention provides aconstrained liner locking ring that can provide a constraining featurefor a polyethylene liner.

Further still, another embodiment of the present invention provides aconstrained liner locking ring that can provide a constraining featurefor a hard bearing surface (e.g., diamond) liner.

Further still, another embodiment of the present invention provides aconstrained liner locking ring in which the geometry of each lockingfeature may be optimized to create the desired mechanical properties forassembly/disassembly (as required).

Further still, another embodiment of the present invention provides aconstrained liner locking ring in which secure fixation of theconstrained liner locking ring allows for optimization of the femoralhead distraction force without the constrained liner locking ringdisassociating from the acetabular cup.

Further still, another embodiment of the present invention provides aconstrained liner locking ring which could be removed (e.g., shouldfemoral head dislocation occur) by applying a clockwise orcounterclockwise motion with a removal instrument. Such easy removal ofthe locking ring would likely not create damage to a well-fixedacetabular cup. After removal of the locking ring, the femoral head maybe reduced and the locking ring re-secured to the acetabular cup.

Further, as described herein, one embodiment of the present inventionprovides a congruency feature (either an interrupted congruency featureor an uninterrupted congruency feature) resulting in an interference fitbetween a liner (e.g., a polyethylene constrained liner) and anacetabular cup (e.g., during initial implantation and subsequentthereto).

Further, in another embodiment of the present invention, theinterference fit between the liner and the acetabular cup may give atactile perception of tightness and/or minimize micro-motion at theliner/acetabular cup interface.

Further still, in one embodiment of the present invention, theinterference fit may provide an improved fit between the liner at roomtemperature and at body temperature.

Referring now to FIGS. 1-13 and 27-34, certain details of a prosthesisaccording to an embodiment of the present invention will be discussed.More particularly, as seen in these Figs., an acetabular cup 101 may beprovided. The cup 101 may comprise an open end and a closed end, whereinthe open end of the cup 101 may be defined by a rim 103 and the rim 103may have an outer facing surface 105. At least one cavity 107 may bedisposed in the rim 103 (one cavity is called out in the Figs., but asseen, a plurality of cavities may be provided), The cavity 107 mayextend from a first end of the cavity at the outer facing surface 105 toa second end of the cavity that is towards the closed end of the cup(cavity 107 may comprise an undercut at the second end of thecavity—see, e.g., FIG. 61).

Further, a locking ring 109 may be provided. At least one tab 111 (onetab is called out in the Figs., but as seen, a plurality of tabs may beprovided) may extend from the locking ring 109. Tab 111 may comprise afirst leg 113 and a second leg 115 having a separation therebetween.Each leg 113, 115 may have a first end and a second end, wherein thefirst end of each leg 113, 115 is at the locking ring 109, wherein thesecond end of the first leg 113 may comprise a tab protrusion 117, andwherein at least the second leg 115 is resilient such that theseparation between the first leg 113 and the second leg 115 is reducedwhen the second leg 115 is deflected towards the first leg.

Further still, the locking ring 109 may be removably locked to the cup101 by placement of the locking ring 109 adjacent the rim 103 andinsertion of the tab 111 into the cavity 107 such that the second leg115 presses against a sidewall of the cavity 107 to initially deflectthe second leg 115 towards the first leg 113 as the tab 111 enters thecavity 107 and the tab protrusion 117 of the first leg 113 is urged intothe undercut in the cavity 107 by the force of the second leg 115subsequently deflecting back away from the first leg 113 (see, e.g.,FIG. 56).

Further still, the locking ring 109 may be unlocked from the cup 101 byrotation of the locking ring 109 relative to the cup 101 such that thesecond leg 115 deflects towards the first leg 113 as the second leg 115is pressed against the sidewall of the cavity 107 and the tab protrusion117 of the first leg 113 is removed from the undercut to allow thelocking ring 107 to be separated from the cup 101 (see, e.g., FIG. 56).

In one example, the first leg 113 may be resilient and the locking ring109 may be removably locked to the cup 101 by placement of the lockingring 109 adjacent the rim 103 and insertion of the tab 111 into thecavity 107 such that the first leg 113 is pressed against the sidewallof the cavity 107 to initially deflect the first leg 113 towards thesecond leg 115 as the tab 111 enters the cavity 107 and the tabprotrusion 117 of the first leg 113 is urged into the undercut by theforce of the first leg 113 as the first leg 113 subsequently deflectsback away from the second leg 115.

In another example, at least a portion of a top surface of the undercutmay be angled to bias the locking ring 109 towards the rim 103 of thecup 101 when the tab protrusion 117 is urged into the undercut (see,e.g., FIG. 56).

In another example, at least a portion of a top surface of the tabprotrusion 117 may be angled to bias the locking ring 109 towards therim 103 of the cup 101 when the tab protrusion 117 is urged into theundercut (see, e.g., FIG. 55).

In another example, a width of the separation between the first leg 113and the second leg 115 may be narrower at a position at the second endof each of the first and second legs 113, 115 relative to a width of theseparation at a position between the second end of each of the first andsecond legs 113, 115 and the first end of each of the first and secondlegs 113, 115 (see, e.g., FIG. 59).

In another example, the prosthesis may further comprise a liner 119,wherein the liner 119 is disposed within the cup 101.

In another example, the prosthesis may comprise a femoral component,wherein the femoral component comprises a ball head 305 and the ballhead 305 is disposed adjacent the liner 307 when the liner 307 isdisposed within the cup 309 (see, FIG. 62). In another example, thefemoral component may further comprise a stem 315 attached to the ballhead 305.

In another example, the ball head 305 may be held within the cup 309 bythe locking ring 301/303.

In another example, the liner may comprise polyethylene.

In another example, cup 101 may have an inner bowl surface, an open endand a closed end; the inner bowl surface may be substantially circularadjacent the open end; and a raised feature 125 may be disposed on theinner bowl surface adjacent the open end of the cup 101 (see, e.g.,FIGS. 6 and 19), wherein the raised feature 125 may be disposed aroundthe circular perimeter of the inner bowl surface (the raised feature 125may provide an interference fit with liner 119 disposed within the cup101).

In another example, the raised feature may be disposed aroundessentially the entire circular perimeter of the inner bowl surface.

In another example, the raised feature may be interrupted at a pluralityof cavities disposed in the inner bowl surface adjacent the open end.

In another embodiment, a prosthesis may be provided, comprising: anacetabular cup, wherein the cup has an open end and a closed end,wherein the open end of the cup is defined by a rim and wherein the rimhas an outer facing surface; a plurality of cavities disposed in therim, wherein each cavity extends from a first end of the cavity at theouter facing surface to a second end of the cavity that is towards theclosed end of the cup, and wherein each cavity comprises an undercut atthe second end of the cavity; a locking ring; and a plurality of tabsextending from the locking ring, wherein each tab comprises a first legand a second leg having a separation therebetween, wherein each leg ofeach tab has a first end and a second end, wherein the first end of eachleg of each tab is at the locking ring, wherein the second end of thefirst leg of each tab comprises a tab protrusion, and wherein at leastthe second leg of each tab is resilient such that the separation betweenthe first leg and the second leg of each tab is reduced when the secondleg of each tab is deflected towards the first leg of each tab; whereinthe locking ring is removably locked to the cup by placement of thelocking ring adjacent the rim and insertion of each tab into arespective one of the cavities such that the second leg of each tabpresses against a sidewall of a respective one of the cavities toinitially deflect the second leg of each tab towards the first leg ofeach tab as each tab enters each respective cavity and each tabprotrusion of the first leg of each tab is urged into the respectiveundercut by the second leg of each tab subsequently deflecting back awayfrom the first leg of each tab.

In one example, the locking ring may be unlocked from the cup byrotation of the locking ring relative to the cup such that the secondleg of each tab deflects towards the first leg of each tab as the secondleg of each tab is pressed against the sidewall of the respective cavityand each tab protrusion of the first leg of each tab is removed from therespective undercut to allow the locking ring to be separated from thecup.

In another example, the first leg of each tab may be resilient and thelocking ring being removably locked to the cup by placement of thelocking ring adjacent the rim and insertion of each tab into arespective one of the cavities may further comprise the first leg ofeach tab being pressed against the sidewall of the respective cavity toinitially deflect the first leg of each tab towards the second leg ofeach tab as each tab enters the respective cavity and each tabprotrusion of the first leg of each tab being urged into the respectiveundercut as the first leg of each tab subsequently deflects back awayfrom the second leg of each tab.

In another example, the number of cavities may equal the integer x, thenumber of tabs may equal the integer x, and the integer x may be between2 and 10, inclusive.

Referring now to FIG. 53, a plan view of an acetabular cup 101Baccording to an embodiment of the present invention is shown. Further,FIG. 54 is a plan view of a constrained liner locking ring 109Aaccording to an embodiment of the present invention. Further still, FIG.55 shows certain details of a tab 111A for locking the locking ring 109Aof FIG. 54 to the cup 101B of FIG. 53. Further still, FIG. 56 is across-sectional view showing certain details of a tab/undercut lockingmechanism for locking the locking ring 109A of FIG. 54 to the cup 101Bof FIG. 53. As seen in these Figs., assembly sight 201 (one assemblysight is called out in the Figs., but as seen, a plurality of assemblysights may be provided) may be used to visually confirm that lockingring 109A is fully secured against cup 101B (e.g., by looking throughthe assembly sight to the cup). Further, the assembly sight(s) may beused as attachment point(s) for one or more tools to assemble and/ordisassemble the locking ring 109A to/from the cup 101B. Further, in thisexample, counter-clockwise rotation of locking ring 109A would be usedto disassemble the locking ring 109A from the cup 101B (of course, theprosthesis could be configured to disassemble upon clockwise rotation ofthe locking ring).

Referring now to FIG. 57, a plan view of the constrained liner lockingring according to another embodiment of the present invention is shown.Further, FIG. 58 shows section A-A with reference to FIG. 57. As seen inthese Figs. groove 203 (one groove is called out in the Figs., but aplurality of grooves may be provided) may be used as attachment point(s)for one or more tools to assemble and/or disassemble the locking ring109A to/from the cup 101B.

Referring now to FIG. 59, certain details of tab 111A for locking thelocking ring of FIG. 54 to the cup of FIG. 53 are shown. Further, FIG.60 shows certain details of tab 111A for locking the locking ring ofFIG. 54 to the cup of FIG. 53. Further still, FIG. 61 shows certaindetails of a cavity undercut in cup 101A used in connection with lockingthe locking ring of FIG. 54 to the cup of FIG. 53. As seen in theseFigs., the length “x” of tab protrusion 117A may be optimized to obtaina desired press-fit for easy assembly and/or disassembly and/or adesired cyclic fatigue rating. Similarly, the thickness “t” of tab legs113A, 115A maybe optimized to obtain a desired press-fit for easyassembly and/or disassembly and/or a desired cyclic fatigue rating (theview of FIG. 60 is 90 degrees offset from the view of FIG. 59). Further,as seen in FIG. 59, the separation between legs 113A, 115A may includewhat is referred to a as “key” to help reduce stress riser and allow fordeflection of leg 113A and/or leg 115A during assembly and/ordisassembly (the “key” may be optimized to obtain a desired press-fitfor easy assembly and/or disassembly and/or a desired cyclic fatiguerating). Of course, “x”, “t” and the size and geometry of the “key” maybe optimized individually or in relation to one another. Finally, asseen in FIG. 61, cavity 107B may include lead in chamfer 205 (to aid inassembly).

Referring now to FIG. 62, a cross-section of a prosthesis according toanother embodiment of the present invention is shown. Further, FIG. 63shows a plan view of an example locking ring of the type used inconnection with the prosthesis of FIG. 62. Further still, FIG. 64 showsanother plan view of an example locking ring of the type used inconnection with the prosthesis of FIG. 62. As seen in these Figs., theuse of a polyethylene or hard bearing constraining ring 301 and alocking ring 303 may provide a mechanism to constrain a hard bearingsurface (e.g., ball 305 and hard bearing surface liner 307) withinacetabular cup 309 for total hip arthroplasty. The polyethylene or hardbearing constraining ring 301 may be placed on the rim of the hardbearing surface liner 307 (e.g., diamond, ceramic, metal) to preventdistraction of the ball 305 from the cup 309. In one example, thepolyethylene or hard bearing constraining ring 301 may have a singleslot 311 to facilitate implantation over the ball (see FIG. 63). Inanother example, the polyethylene or hard bearing constraining ring 301may have multiple slots 313 (one slot is called out in the Figs., but asseen, a plurality of slot may be provided), which may be determined by adesired assembly force (see FIG. 64). In one specific example, there maybe 2, 4 or 6 multiple partial slots. Further, the prosthesis maycomprise stem 315.

Referring now to FIG. 65, a plan view of an acetabular cup according toan embodiment of the present invention is shown. Further, FIG. 66 showsa cross-section of an example interference fit feature of the acetabularcup of FIG. 65. Further still, FIG. 67 shows another cross-section of anexample interference fit feature of the acetabular cup of FIG. 66. Asseen in these Figs., to improve congruency (fit) of a polyethylene linerat room temperature, a raised feature 125B is provided. In one example,this raised feature 125B is interrupted by the anti-rotation notches inthe cup 101C.

The raised feature (“blip” located just below the face of the acetabularcup at the opening of the acetabular cup) creates interference betweenthe acetabular cup and the liner. In this example, the liner has acontinuous diameter slightly larger than the diameter created by the“blip” to create an interference fit between the two parts. In thisexample, there are twelve “blips” located inside of the acetabular crowncup due to the interruptions created for the anti-rotation feature (anydesired number other than 12 may, of course, be used). In one example,the length of the “blip” feature may be held constant for all cupdiameters so that essentially the same insertion force range isexperienced during implantations. The insertion force can be optimizedfor a particular application by increasing or decreasing the “blip”length and/or the amount of interference between the “blip” and theliner.

Of note, the raised feature discussed above may provide a surgeon withthe perception that a polyethylene liner for an acetabular cup is tightor fully congruent at room temperature (the typical reality is that thepolyethylene liner will expand/grow to produce a tight fit between thepolyethylene liner and the metal acetabular cup once the system hasstabilized to body temperature (about 37° C.), provided that the initialfit is reasonably tight).

Of further note, a highly congruent polyethylene liner against a metalsupport (e.g., acetabular cup) may be key to evenly distributingstresses developed in the polyethylene liner from normal joint forces.If two mating parts (one polyethylene and the other metal) are notcongruent, the polyethylene will cold flow to find an equilibrium state.The cold flow event creates changes in the liner geometry to compensatefor differences in the mating geometries.

Referring now to FIG. 68, this shows a cross-section of an exampleinterference fit feature of a polyethylene liner. More particularly, asseen in this Fig., constrained liner 119B may include a depression or araised portion (“congruency feature) for providing an interference fitwith an acetabular cup.

While a number of embodiments of the present invention have beendescribed, it is understood that these embodiments are illustrativeonly, and not restrictive, and that many modifications may becomeapparent to those of ordinary skill in the art. For example, any elementdescribed herein may be provided in any desired size (e.g., any elementdescribed herein may be provided in any desired custom size or anyelement described herein may be provided in any desired size selectedfrom a “family” of sizes, such as small, medium, large). Further, one ormore of the components may be made from any of the following materials:(a) any biocompatible material (which biocompatible material may betreated to permit surface bone ingrowth or prohibit surface boneingrowth—depending upon the desire of the surgeon); (b) a plastic; (c) afiber; (d) a polymer; (e) a metal (a pure metal such as titanium and/oran alloy such as Ti—Al—Nb, Ti-6Al-4V, stainless steel); (f) anycombination thereof Further still, any metal construct may be a machinedmetal construct. Further still, any number of protrusions (e.g., such asfor initial fixation by forming a bond with cement and/or such as forsupplemental fixation by forming a bond with cement) may be utilizedwith a given prosthesis. Further still, any number of female featuresthat increase the cement mantle may be utilized with a given prosthesis.Further still, any number of male features that could dig into the boneso that initial/supplemental fixation can be improved may be utilizedwith a given prosthesis. Further still, any number of bone screws (e.g.,such as for initial fixation and/or such as for supplemental fixation)may be utilized with a given prosthesis. Further still, any stepsdescribed herein may be carried out in any desired order (and anyadditional steps may be added as desired and/or any steps may be deletedas desired).

1. A prosthesis, comprising: an acetabular cup, wherein the cup has anopen end and a closed end, wherein the open end of the cup is defined bya rim and wherein the rim has an outer facing surface; at least onecavity disposed in the rim, wherein the cavity extends from a first endof the cavity at the outer facing surface to a second end of the cavitythat is towards the closed end of the cup, and wherein the cavitycomprises an undercut at the second end of the cavity; a locking ring;and at least one tab extending from the locking ring, wherein the tabcomprises a first leg and a second leg having a separation therebetween,wherein each leg has a first end and a second end, wherein the first endof each leg is at the locking ring, wherein the second end of the firstleg comprises a tab protrusion, and wherein at least the second leg isresilient such that the separation between the first leg and the secondleg is reduced when the second leg is deflected towards the first leg;wherein the locking ring is removably locked to the cup by placement ofthe locking ring adjacent the rim and insertion of the tab into thecavity such that the second leg presses against a sidewall of the cavityto initially deflect the second leg towards the first leg as the tabenters the cavity and the tab protrusion of the first leg is urged intothe undercut by the second leg subsequently deflecting back away fromthe first leg.
 2. The prosthesis of claim 1, wherein the locking ring isunlocked from the cup by rotation of the locking ring relative to thecup such that the second leg deflects towards the first leg as thesecond leg is pressed against the sidewall of the cavity and the tabprotrusion of the first leg is removed from the undercut to allow thelocking ring to be separated from the cup.
 3. The prosthesis of claim 1,wherein: the first leg is resilient; and the locking ring beingremovably locked to the cup by placement of the locking ring adjacentthe rim and insertion of the tab into the cavity further comprises thefirst leg being pressed against the sidewall of the cavity to initiallydeflect the first leg towards the second leg as the tab enters thecavity and the tab protrusion of the first leg being urged into theundercut as the first leg subsequently deflects back away from thesecond leg.
 4. The prosthesis of claim 1, wherein at least a portion ofa top surface of the undercut is angled to bias the locking ring towardsthe rim of the cup when the tab protrusion is urged into the undercut.5. The prosthesis of claim 1, wherein at least a portion of a topsurface of the tab protrusion is angled to bias the locking ring towardsthe rim of the cup when the tab protrusion is urged into the undercut.6. The prosthesis of claim 1, wherein a width of the separation betweenthe first leg and the second leg is narrower at a position at the secondend of each of the first and second legs relative to a width of theseparation at a position between the second end of each of the first andsecond legs and the first end of each of the first and second legs. 7.The prosthesis of claim 1, further comprising a liner, wherein the lineris disposed within the cup.
 8. The prosthesis of claim 7, furthercomprising a femoral component, wherein the femoral component comprisesa ball head and the ball head is disposed adjacent the liner when theliner is disposed within the cup.
 9. The prosthesis of claim 8, whereinthe ball head is held within the cup by the locking ring.
 10. Theprosthesis of claim 7, wherein the liner comprises polyethylene.
 11. Aprosthesis, comprising: an acetabular cup, wherein the cup has an openend and a closed end, wherein the open end of the cup is defined by arim and wherein the rim has an outer facing surface; a plurality ofcavities disposed in the rim, wherein each cavity extends from a firstend of the cavity at the outer facing surface to a second end of thecavity that is towards the closed end of the cup, and wherein eachcavity comprises an undercut at the second end of the cavity; a lockingring; and a plurality of tabs extending from the locking ring, whereineach tab comprises a first leg and a second leg having a separationtherebetween, wherein each leg of each tab has a first end and a secondend, wherein the first end of each leg of each tab is at the lockingring, wherein the second end of the first leg of each tab comprises atab protrusion, and wherein at least the second leg of each tab isresilient such that the separation between the first leg and the secondleg of each tab is reduced when the second leg of each tab is deflectedtowards the first leg of each tab; wherein the locking ring is removablylocked to the cup by placement of the locking ring adjacent the rim andinsertion of each tab into a respective one of the cavities such thatthe second leg of each tab presses against a sidewall of a respectiveone of the cavities to initially deflect the second leg of each tabtowards the first leg of each tab as each tab enters each respectivecavity and each tab protrusion of the first leg of each tab is urgedinto the respective undercut by the second leg of each tab subsequentlydeflecting back away from the first leg of each tab.
 12. The prosthesisof claim 11, wherein the locking ring is unlocked from the cup byrotation of the locking ring relative to the cup such that the secondleg of each tab deflects towards the first leg of each tab as the secondleg of each tab is pressed against the sidewall of the respective cavityand each tab protrusion of the first leg of each tab is removed from therespective undercut to allow the locking ring to be separated from thecup.
 13. The prosthesis of claim 11, wherein: the first leg of each tabis resilient; and the locking ring being removably locked to the cup byplacement of the locking ring adjacent the rim and insertion of each tabinto a respective one of the cavities further comprises the first leg ofeach tab being pressed against the sidewall of the respective cavity toinitially deflect the first leg of each tab towards the second leg ofeach tab as each tab enters the respective cavity and each tabprotrusion of the first leg of each tab being urged into the respectiveundercut as the first leg of each tab subsequently deflects back awayfrom the second leg of each tab.
 14. The prosthesis of claim 11, whereinthe number of cavities equals the integer x, the number of tabs equalsthe integer x, and the integer x is between 2 and 10, inclusive.
 15. Aprosthesis, comprising an acetabular cup, wherein the cup has an innerbowl surface, an open end and a closed end, and wherein the inner bowlsurface is substantially circular adjacent the open end; and a raisedfeature disposed on the inner bowl surface adjacent the open end of thecup, wherein the raised feature is disposed around the circularperimeter of the inner bowl surface; wherein the raised feature providesan interference fit with a liner disposed within the cup.
 16. Theprosthesis of claim 15, wherein the raised feature is disposed aroundessentially the entire circular perimeter of the inner bowl surface. 17.The prosthesis of claim 15, wherein the raised feature is interrupted ata plurality of cavities disposed in the inner bowl surface adjacent theopen end.